The present invention relates to a photographing apparatus connected to another electronic device and power supply method.
1. Prior Art
The USB (Universal Serial Bus) Standard has come into widespread use as an interface standard for communication between a personal computer and its peripheral equipment connected thereto. The USB Standard was worked out by a plurality of business companies and has come to be released to the public. For example when connection is made between a personal computer and a photographing apparatus such as a digital camera according to this USB Standard, the personal computer works as a host machine, while the digital camera as peripheral equipment acts as a slave. The personal computer as a host provides power required for communications between two pieces of equipment.
To supplement the USB Standard, the USB OTG (On The Go) Standard for connection among pieces of peripheral equipment is established. According to the OTG Standard, peripheral equipment working merely as a slave under the USB Standard is provided with the functions of a host. This allows the peripheral equipment to be connected with other peripheral equipment without the aid of a personal computer, whereby communications are established among different pieces of peripheral equipment. For example, when a digital camera is used as peripheral equipment functioning as a host, image data can be transferred to the printer for printing by connection between the digital camera and a printer, the image data can be recorded into the storage apparatus of the PDA by connection between the digital camera and a PDA, or the network can be accessed by connection between the digital camera and cellular phone, so that image data can be sent directly from the digital camera.
When peripheral equipment is connected to another piece of peripheral equipment, one of them functions as a host while the other works as a slave, so power required for communications is supplied from the host to the slave. Accordingly, when the digital camera is used as a host for example, power required for communications is supplied from the digital camera.
2. Problems to be Solved by the Invention
According to the power supply method in a prior art photographing apparatus, however, if a digital camera is used as a host for example, power for communications is continuously supplied to the peripheral equipment throughout the operation of the digital camera even when there is no communication with the connected peripheral equipment. This has led to waste of digital camera power supply. A digital camera normally uses a battery to supply power, and waste of power has raised the problem of an ineffective use of the battery power.
Thus, the object of the present invention is to provide a photographing apparatus that ensures an effective supply of power for communications carried out by connection between pieces of peripheral equipment.